smog

noun

ˈsmäg 

ˈsmȯg

: a fog made heavier and darker by smoke and chemical fumes

also : a photochemical haze caused by the action of solar ultraviolet radiation on atmosphere polluted with hydrocarbons and oxides of nitrogen especially from automobile exhaust

smogless

ˈsmä-gləs 

ˈsmȯ-

adjective

Synonyms

• brume
• fog
• gauze
• haze
• mist
• murk
• reek
• soup

Examples of smog in a Sentence

the city's smog was once so bad that darkness often prevailed, even at noon

Recent Examples on the Web

The state’s efforts to reduce smog in Southern California led to the use of catalytic converters and emissions treatment technology that have worked wonders in making auto exhaust much less dangerous. —Alan Ohnsman, Forbes.com, 16 June 2025

The pollution also creates ground-level ozone when nitrogen oxides and volatile organic compounds — emissions from vehicles — bake in the heat and form a brown smog over the Front Range. —Noelle Phillips, Denver Post, 13 June 2025

The green house gas rating is a 9, and the smog rating is a 6, both out of 10. —Tony Leopardo, Mercury News, 9 June 2025

By comparison, cars in the region currently emit about 9 tons of NOx per day, Martinez said. NOx isn’t only responsible for smog. —Hayley Smith, Los Angeles Times, 4 June 2025

Word History

Etymology

smoke + fog

First Known Use

1880, in the meaning defined above

Phrases Containing smog

• anti-smog

Rhymes for smog

• blog
• bog
• clog
• cog
• dog
• flog
• fog
• frog
• grog
• hog
• jog
• log

Kids Definition

smog

noun

ˈsmäg 

 also  ˈsmȯg

: a thick haze caused by the action of sunlight on air polluted especially by smoke and automobile exhaust fumes

Etymology

from smoke and fog

Medical Definition

smog

noun

ˈsmäg also ˈsmȯg

: a fog made heavier and darker by smoke and chemical fumes

also : a photochemical haze caused by the action of solar ultraviolet radiation on atmosphere polluted with hydrocarbons and oxides of nitrogen especially from automobile exhaust